Ask your vet. Panacur is a very mild drug, but to much of a good thing can be bad.
I have never heard of anyone using anything to put back good bacteria w/ the use of Panacur.
I would also recommend the use of Flagyl in addition. Your vet can get you the propper dose of that as well.
You will need to get the weight on each. I would also recommend taking a fecal sample in to your vet before giving the meds. You may not need them.
In Highfield's book, he gives you the correct dosage. you may be able to get the coorect dosage from the Tortoise Trust web page. Please consult your vet before giving any med!